Background/rationale: Tremor is the second most common complaint in patients with Parkinson's disease (PD) after slowness, as it is bothersome to patients and interferes with many hand functions (e.g. eating, buttoning, zipping, shaving, typing, handling pills, tying shoelace, and brushing teeth). Muscle weakness is also a consequence of slowness and contributes to impaired fine movements and manual dexterity. Patients with pronounced tremor are disabled by the tremor itself and may suffer from social isolation that further decreases quality of life. Postural tremor can limit activities of daily living (ADL). Pronounced tremor can impair fine motor dexterity as well as job performance. In such cases, the tremor results in handicap and disability. Previous evidence demonstrated that resistance training significantly reduced motor unit firing rate variability, reduced upper limb coactivation, improved digit force steadiness, and improved intra- and intermuscular coordination, factors which could improve tremor and movement control in persons with neurological conditions. There has been no study on a rehabilitation intervention for impaired hand dexterity and tremor in PD. Project objectives: In this project, the investigators (Dr. Bryant and her research team) will study the effect of progressive resistance exercise of hand and arm (HREX) on hand dexterity and tremor in patients with PD. The specific purposes of this proposal are to: 1) Estimate the efficacy of HREX to improve hand dexterity, and strength; 2) Estimate the efficacy of HREX in reducing tremor and bradykinesia; and 3) Estimate the efficacy of HREX to reduce motor impairments from PD and ADL. Project methods: This study is a randomized wait-list controlled design using 6 weeks of HREX, as a home-based program. 62 Veterans with a diagnosis of PD will be recruited and randomized into wait-list control (WAIT) and exercise (HREX) groups. Subjects will use a dumbbell, a hand grip, and hand therapy putty to exercise at home. Volume of exercise (sets and repetitions) will be increased to gradually progress the exercises during the 6 weeks. The subjects will be asked to do the exercise 3 times a week on 3 different days, with at least 24- hour intervals between sessions. The WAIT group will start their exercise at the end of a 6- week waiting period. Measures to evaluate the efficacy are tremor amplitude, finger tapping test, Purdue pegboard test, electromyography (EMG), tremor clinical rating score, grip strength, motor and activity of daily living (ADL) scores. Long-term objectives: If efficacy of the resistanc exercise is demonstrated, the team will develop a larger multi-center proposal to implement this intervention in clinical care to benefit Veterans suffering from PD. The home-based, strengthening exercise program can be used as an adjunct to medical treatment in Veterans with PD.